Marimba Body: Thumbs

Thumbs.

Without them who knows how we'd play our instruments.

Interest in the relationship between the hand, wrist, and thumb began a few years ago when I took piano lessons to refine my technique. (As similar as piano and percussion are in theory, there's much less crossover than I mistakenly thought and hoped.)  

Anyway, something my mentor said was when the thumb isn't being used it should relax towards the rest of the hand and fingers.  Sure, may sound obvious, but in the throes of playing - piano or percussion - it's easy to forget little things like this. 

Brain: Play a broken 13 over 7, across 6 surfaces...crescendo...oh, right. THUMB.

End Scene

Thumbs that are mis-mapped, working more than they should, or working when they don't need to contribute to funny aches, pains, and numbness that can get mistaken for carpal tunnel.  

Just like all other subjects in the Marimba Body series, how we relate to the structure and movement design of the thumb is evident in the effectiveness of technique and absence or presence of discomfort.

Skeletal Structure

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From the fingertips, the bones of the hand are the phalanges (3 in the index-pinky fingers; 2 in the thumb), metacarpals (5 of them - one for each finger), and the carpals, which articulate the wrist joint.  Disclaimer about the diagram: the ulna doesn't actually contact the carpals. There's space between.

  

While the metacarpals of the four fingers are within our palm, the metacarpal of the thumb aligns outside it, giving the digit a much larger range of motion and greater independence than the others.  You can try to feel the length of that metacarpal with your fingertips: anything that moves around is a tendon, but if you imagine the shape of the bone as you feel, you might be able to get a sense of how far down that metacarpal goes.

Ligaments and Tendons

Ligaments connect bone to bone, and are unbelievably strong: bones break before ligaments break, if that's any indication.

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The two drawings above are of a right hand: upper left shows posterior (back of the hand), bottom right shows anterior (palm).  The labels of ligaments are too small to read, but that's ok for our purposes, as we just need to look at them.  

Ligaments above are drawn as white bands.  Along each finger they connect phalanges to one another and to the respective metacarpal.  Notice how much thicker they appear to be on the palm side of the hand; really, this makes sense considering the muscle is located here.  

Very important is the ligament running horizontally across the metacarpals of the index-pinky fingers.  This Deep Transverse Metacarpal ligament shapes the top of the palm.  

Physiologically, it stabilizes the palm and makes the job of our small hand muscles easier: imagine if we had to control each finger from the wrist rather than the top of the palm - talk about carpal tunnel and injuries.

There's obviously something that keeps the thumb connected to the palm, and that's the job of muscles and tendons.

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Above, tendons are white and muscle tissue is red.  Looking at the thumb, it's clear that its phalangeal length contains no actual muscle, only tendons, ligaments, and bone. (Well, and veins and stuff, but that's not the point right now.)  The vast majority of muscle within the hand that moves our thumb is on the anterior side, near the wrist. We all remember aches there in school as we furiously took notes. Guitar and string players are probably keenly aware of this muscle, and tend to have the largest bulge there of all musicians.  

Knowing the location of muscle is key in determining if the body is being used correctly.  If you try to move your thumb from a muscle you imagine to be at its second knuckle, you will quickly get sore, as there's no muscle there to move, only tendon to swell.

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This diagram shows flexor muscles that help move the thumb toward the palm. If you try, you can feel the muscles working all the way up your forearm.  Similarly, to extend the thumb up or stretch it away from the palm involves muscles of the forearm, though not all are shown here. 

To isolate thumb movement as something that only happens in the digit itself is misleading, and, for a professional musician, dangerous. 

Habit to Avoid 

One of the main culprits of pain at the base of the thumb is keeping it outstretched for long periods of time.  Though I encountered this problem first on piano, it applies to 4-mallet playing, too.  This post, by pianist Graham Fitch, is really enlightening when it comes to causes of thumb injury.It takes more energy to hold a large interval than it does a small one. And depending on how you habitually work your thumbs, your own "default" interval may tell you whether or not you are overworking the thumb.  If your "default" is larger than a 4th or 5th, you're probably overworking the thumb.  This is visually more relevant to cross-grip players.  

Since the mechanism for Musser and Stevens grips is different from the cross grips, thumb issues there are more about locking joints than overworking.  For example, a thumb whose tip points up towards the player - ie: hitchhiker thumb - is overstretching the anterior ligament between the phalanges and compressing the tendon on the posterior side. Eventually, numbness may set in as a result.  

Another place thumbs can cause trouble is in hand-drumming.  Slamming the thumb down on the rim of a conga is quite unpleasant, and so we talk at length about finger/hand position.  It bogs us down and locks us up rather than encouraging the free feeling innate to hand drumming.  Relax the thumb towards the palm, align the wrist, and away we go.

Normal Variants

From person to person there are many variants in the size and characteristics of thumbs.  Some of us have "toe thumbs" with wide tips, others have narrow tips, some are thin and willowy and others are rather stocky.  None of this is weird: it all falls within the category of normal variants, or arbitrary differences between us that don't affect quality of use.  Other examples are hair and eye color.  

I have a theory, though, that these idiosyncrasies are some of the things that determine nuances of our own technique, or even what technique best suits a player. For example, I have really long thumbs.  They don't move better or worse than short thumbs, they're just long.  Normal variant = long thumb

The first 4-mallet grip I learned was Stevens, but in comparing my hands to photos in MOM it didn't look right, and I was somehow stretching my index finger out too far.  Well, guess what, y'all, when ya got long thumbs, the only way to make a fulcrum is to outstretch an index finger. 

Check it out:

thumb length forces the index to partially extend

longer thumb makes securing an interval easier

This stretching really taxed the small muscles in my hand, and made playing something I wanted to do but never enjoyed due to discomfort.  In trying to make my hands match someone else's in form rather than function, I started to compress and lock joints in my hand.  My long thumbs don't make me a bad player - in fact, they make big intervals easier, to a certain degree - but they did tell me, through discomfort, that they were more suited to a cross grip.  It's that easy, and that non-controversial.  A 3-finger fulcrum suits me better, too, all because it more closely maintains a relaxed hand/thumb relationship.  

Our normal variants are the things that make us unique, and, I believe, contribute to our personal sound.  They are things to be embraced, not to wish were different or manipulate into working a different way than designed.  

I'd love to know if others out there have changed technique or adjusted a current one to fit idiosyncrasies, too.  Consider it a bit of informal research - I'd like to report on this for our podcast in the coming weeks!